In the past, roll control devices for projectiles used either reaction jets and/or actuated aerodynamic surfaces. However, the use of such devices has presented several drawbacks. First, the devices generally included explosive elements or other high pressure devices. As those skilled in the art will appreciate, the use of explosives tends to disturb the projectile trajectory. Additionally, the use of propellant creates a limiting time factor to the control of the projectile, due to the predetermined burn time of the quantity of propellant stored on the projectile.
U.S. Pat. Nos. 4,568,039 and 4,438,893 disclose a guidance system for a spinning projectile. In the disclosed system the main housing spins and a front canard frame is despun. Two stator windings are disposed within the main housing and a cooperative pair of rotors are arranged within the canard frame. The first stator winding and rotor set generate power to provide control of the rotational position of the canard frame. The second stator winding and rotor set generates power for control of the deflectable canards. The disclosed device, however, includes several drawbacks. First, the device requires that the spin be imparted on the projectile by the launching device. By imparting the spin upon launch, the amount of energy available is limited and decreases over the duration of the flight. This is especially true while utilizing the spin for the purpose of despinning the front canard frame and generating power for the deflectable canards to steer the shell. In order to store the necessary energy a large rotational mass for the main housing must be used.
Therefore, there is a need for a new and improved roll control device which minimizes disturbance to the projectile trajectory, and provides on-demand, available torque for roll control during the entire projectile flight--for a variety of flight lengths.